Field of the Invention
An embodiment of the present invention relates to a charged particle image measuring device and an imaging mass spectrometry apparatus.
Description of the Related Art
“Imaging mass spectrometry” is receiving attention as a technique for detecting substance distribution of a biological sample. In general, mass spectrometry is a method that ionizes a sample by irradiating the sample with a primary beam of laser light, ions, or electrons, separates ions emitted from the sample by their mass-to-charge (m/z) ratios, and obtains a spectrum consisting of mass-to-charge ratios and detected intensity thereof. In imaging mass spectrometry, the surface of a sample is two-dimensionally mass-analyzed, and the distribution of substances on the surface of the sample, that is, “mass image” is obtained.
There are two types of methods of imaging in imaging mass spectrometry: a scanning type imaging mass spectrometry and a projection type imaging mass spectrometry.
The scanning type imaging mass spectrometry is a method that sequentially mass-analyzes micro regions on a sample, and reconstructs a mass image from the result of mass spectrometry and the positional information of the micro regions. In the scanning type, spatial resolution depends on the size or the like of micro regions, and is determined by the beam diameter of the primary beam and the scanning position accuracy of the primary beam.
In the projection type imaging mass spectrometry, predetermined regions on a sample are collectively ionized, and an image of emitted ions is formed on a two-dimensional detector by a charged particle lens. In the projection type imaging mass spectrometry, emitted ions from the surface of the sample are also mass separated while the ions are flying, eventually mass images are obtained (PCT Japanese Translation Patent Publication No. 2014-514591). The spatial resolution in the projection type imaging mass spectrometry is determined by the accuracy of measurement of ion arrival position in the two-dimensional detector and the magnification, aberration, and the like of the charged particle lens.
High spatial resolution has been desired in imaging mass spectrometry.